springboot的JPA在Mysql8新增记录失败
springboot版本是1.3.0.M1，连接的mysql版本为8，用spring-boot-starter-data-jpa操作数据库，新增记录时应用抛出以下异常：
2018-02-21 12:52:59.471 DEBUG 6408 --- [nio-9090-exec-1] o.s.web.servlet.DispatcherServlet : Could not complete requestorg.springframework.orm.jpa.JpaSystemException: could not execute statement; nested exception is org.hibernate.exception.GenericJDBCException: could not execute statementat org.springframework.orm.jpa.vendor.HibernateJpaDialect.convertHibernateAccessException(HibernateJpaDialect.java:310)at org.springframework.orm.jpa.vendor.HibernateJpaDialect.translateExceptionIfPossible(HibernateJpaDialect.java:221)at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.translateExceptionIfPossible(AbstractEntityManagerFactoryBean.java:417)at org.springframework.dao.support.ChainedPersistenceExceptionTranslator.translateExceptionIfPossible(ChainedPersistenceExceptionTranslator.java:59)at org.springframework.dao.support.DataAccessUtils.translateIfNecessary(DataAccessUtils.java:213)at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:147)at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)at org.springframework.data.jpa.repository.support.CrudMethodMetadataPostProcessor$CrudMethodMetadataPopulatingMethodInterceptor.invoke(CrudMethodMetadataPostProcessor.java:121)at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92)at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:207)at com.sun.proxy.$Proxy74.save(Unknown Source)at com.business.backend.dao.impl.BaseStockDaoImpl.save(BaseStockDaoImpl.java:24)at com.business.backend.controller.BaseStockController.savePost(BaseStockController.java:78)at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)at java.lang.reflect.Method.invoke(Method.java:498)at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221)at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:137)at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:111)at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:799)at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:728)at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959)at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893)at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:969)at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:871)at javax.servlet.http.HttpServlet.service(HttpServlet.java:648)at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:845)at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77)at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:85)at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142)at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518)at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091)at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:668)at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1521)at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1478)at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)at java.lang.Thread.run(Thread.java:745)Caused by: org.hibernate.exception.GenericJDBCException: could not execute statementat org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:54)at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:126)at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:112)at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:211)at org.hibernate.id.IdentityGenerator$GetGeneratedKeysDelegate.executeAndExtract(IdentityGenerator.java:96)at org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:58)at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:3032)at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:3558)at org.hibernate.action.internal.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:98)at org.hibernate.engine.spi.ActionQueue.execute(ActionQueue.java:492)at org.hibernate.engine.spi.ActionQueue.addResolvedEntityInsertAction(ActionQueue.java:197)at org.hibernate.engine.spi.ActionQueue.addInsertAction(ActionQueue.java:181)at org.hibernate.engine.spi.ActionQueue.addAction(ActionQueue.java:216)at org.hibernate.event.internal.AbstractSaveEventListener.addInsertAction(AbstractSaveEventListener.java:334)at org.hibernate.event.internal.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:289)at org.hibernate.event.internal.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:195)at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:126)at org.hibernate.jpa.event.internal.core.JpaPersistEventListener.saveWithGeneratedId(JpaPersistEventListener.java:84)at org.hibernate.event.internal.DefaultPersistEventListener.entityIsTransient(DefaultPersistEventListener.java:206)at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:149)at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:75)at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:811)at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:784)at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:789)at org.hibernate.jpa.spi.AbstractEntityManagerImpl.persist(AbstractEntityManagerImpl.java:1181)at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)at java.lang.reflect.Method.invoke(Method.java:498)at org.springframework.orm.jpa.ExtendedEntityManagerCreator$ExtendedEntityManagerInvocationHandler.invoke(ExtendedEntityManagerCreator.java:344)at com.sun.proxy.$Proxy64.persist(Unknown Source)at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)at java.lang.reflect.Method.invoke(Method.java:498)at org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:291)at com.sun.proxy.$Proxy64.persist(Unknown Source)at org.springframework.data.jpa.repository.support.SimpleJpaRepository.save(SimpleJpaRepository.java:439)at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)at java.lang.reflect.Method.invoke(Method.java:498)at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.executeMethodOn(RepositoryFactorySupport.java:452)at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.doInvoke(RepositoryFactorySupport.java:437)at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.invoke(RepositoryFactorySupport.java:409)at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)at org.springframework.data.projection.DefaultMethodInvokingMethodInterceptor.invoke(DefaultMethodInvokingMethodInterceptor.java:61)at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:99)at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:281)at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:136)... 54 common frames omittedCaused by: java.sql.SQLException: Could not retrieve transation read-only status serverat com.mysql.jdbc.SQLError.createSQLException(SQLError.java:998)at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:937)at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:926)at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:872)at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:904)at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:894)at com.mysql.jdbc.ConnectionImpl.isReadOnly(ConnectionImpl.java:3613)at com.mysql.jdbc.ConnectionImpl.isReadOnly(ConnectionImpl.java:3582)at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2111)at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2081)at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2066)at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:208)... 103 common frames omittedCaused by: java.sql.SQLException: Unknown system variable 'tx_read_only'at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:998)at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3835)at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3771)at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2435)at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2582)at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2531)at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2489)at com.mysql.jdbc.StatementImpl.executeQuery(StatementImpl.java:1446)at com.mysql.jdbc.ConnectionImpl.isReadOnly(ConnectionImpl.java:3607)... 108 common frames omitted
这一句是关键信息：Unknown system variable ‘tx_read_only’，应该是mysql-connector-java的jar包的版本和数据库不匹配导致的；
当前的springboot项目是个maven工程，打开pom.xml文件看一下mysql-connector-java库的依赖：
<dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId></dependency>
如上所示，pom.xml中没有指定mysql-connector-java库的版本，我们只能用mvn命令查看默认版本是多少了，在pom.xml所在目录下执行以下命令，查看所有jar包的版本信息：
mvn dependency:tree
在输出的信息中看到了mysql-connector-java的版本是5.1.35，如下：
[INFO] +- mysql:mysql-connector-java:jar:5.1.35:compile
5.1.35版本偏高了，我们还是在pom.xml中指定一个低版本吧，修改mysql-connector-java库的依赖配置如下：
<dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>5.1.15</version></dependency>
如果您用的IDE是IntelliJ IDEA，修改上面的配置可能不会立即生效，请在pom.xml文件上点右键，选”Maven”->“Reimport”，如下图：
再次启动springboot应用并新增记录到mysql，这次一切顺利了。
spring data jpa + mysql 上踩过的坑
最近在做一个小项目，技术上用的是springboot+jpa(Java Persistence API)
spring data jpa让我们解脱了DAO层的操作，基本上所有CRUD都可以依赖于它来实现，他是实现了orm思想的一套框架。
（1）先让实体类和数据库表对应，再让实体类属性和表里面字段对应
@Entity@Table(name = "t_user")public class User { @Id @GeneratedValue private Long id; private String nickname; private String username; private String password; getter and setter...}
（2）不需要直接操作数据库表，直接操作表对应的实体类对象
public interface UserRepository extends JpaRepository<User,Long> { User findByUsernameAndPassword(String username, String password);}
好了，问题就出在这第一步里的实体类属性和表里面字段对应
注意这个注解 @GeneratedValue ，他共有四种取值：（strategy = ***）
AUTO主键由程序控制, 是默认选项 ,不设置就是这个 IDENTITY 主键由数据库生成, 采用数据库自增长, Oracle不支持这种方式 SEQUENCE 通过数据库的序列产生主键, MYSQL 不支持 Table 提供特定的数据库产生主键, 该方式更有利于数据库的移植
以下是我今天解决问题过程中的一些想法，不一定对，仅供参考
在对应主键字段的属性上要是只标注了@GeneratedValue那就意味着把主键的生成策略交给了springboot，它将自动的判断你所使用的数据库，若是Mysql则设置成IDENTITY，Oracle则设置成SEQUENCE。
但我今天是用jpa自动生成的数据库
最上面举的实体类的例子也正是我编写实体类采用的注解方式，下面是我定义的实体类一共五个。
由于其中两个类之间的关系是多对多，所以按道理最终生成的表应该是六张，也就是五张实体类对应表和一张中间表。但实际情况确实这样的：
没错，他多了一张表！多了一张貌似相当于Oracle中的序列表（我也不太懂Oracle…就是觉得长的像）这张表只有一个字段，并且其他几张表的主键自增长都没有打开
就是指定了你下一个自动生成的主键的值，关键是所有表共用这个序列表，举个例子：
A表插入一条数据后自动生成的id=10，接下来你取B表插入一条数据，他生成的id就一定会接下去（=11）
如果你先在数据库中手动创建几条数据，让id的值超过序列表中的值
然后在项目系统中使用增加数据功能时就会…
Caused by: java.sql.SQLIntegrityConstraintViolationException: Duplicate entry ‘13′ for key ‘PRIMARY’
破坏了完整性约束，在这里也就是说表中出现了重复的主键id=13,然后我不干任何事，在系统中再次执行我的添加功能：
Caused by: java.sql.SQLIntegrityConstraintViolationException: Duplicate entry ‘14′ for key ‘PRIMARY’
那个序列表就会自增1然后再添加，发现id=14又已经存在了。相信大家已经看懂这序列表的机制了吧，就是说只要我在系统中在执行一次添加功能，这条数据就能够被加进数据库里了。
这样也太麻烦了吧，解决它其实很简单，只要在实体类中手动指定主键的生成策略，并且将表中对应主键字段的 自动递增打开 就行了，springboot就会放弃那张序列表而按照你指定的方式去生成主键了：
@Entity@Table(name = "t_user")public class User { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id; private String nickname; private String username; private String password;
以上为个人经验，希望能给大家一个参考，也希望大家多多支持。
没有早一步，也没有晚一步，刚好遇上了你！
